The present invention relates to an electromagnetic valve actuator having a single electromagnetic coil positioned between two magnetic armature plates for opening and closing a valve in a vehicle engine.
In a vehicle engine, a valve is controlled to open and close so that a cylinder may perform intake, compression, expansion, and exhaust operations.
In one example of a drive apparatus for opening and closing valves, a camshaft, which is configured by disposing cams for vale opening and closing on one shaft, is provided on the upper portion of the engine or on one side face thereof. A crankshaft, which translates the piston motion to rotational motion, and the camshaft which operates the vales are connected by means such as a belt or chain. The camshaft is driven in synchronism with the crankshaft of the engine. The valves are opened by the cam lobes on the camshaft via a link mechanism such as a rocker arm or push rod. The valve normally is held in the closed position by a spring.
In another example of a drive apparatus for opening and closing an intake exhaust valve, an intake camshaft having an intake valve opening profile, and an exhaust camshaft having an exhaust valve opening profile are disposed on the upper portion of an engine, the cam lobe of the intake camshaft pushes the axial end face other intake valve directly, and the cam lobe of the exhaust camshaft pushes the axial end face of the exhaust valve directly, thereby opening the intake/exhaust valve.
This conventional drive apparatus for opening and closing the intake/exhaust valve results in an increase in engine size because the camshaft and link mechanism must be added onto the engine. Furthermore, since the camshaft and link mechanism are driven by the output shaft (crankshaft) of the engine, some of the engine output is consumed by frictional resistance when the camshaft and link mechanism are driven. This reduces the effective output of the engine.
Further, the actuation timing of the intake/exhaust valve is fixed and cannot be altered during engine operation. Hence, the valve actuation timing is a compromise between low and high engine rpm. As a consequence, the engine output torque is not optimum neither at low nor at high engine rpm.
In order to solve the foregoing problems, various systems for driving an intake/exhaust valve to open and close the same by electromagnetic force from an electromagnet, without relying upon a camshaft, have been proposed, such as in U.S. Pat. Nos. 4,955,334 and 4,829,947, which are both hereby incorporated by reference in their entirety. These patents teach the use of a single armature plate which is movable by a pair of electromagnetic coils positioned on opposing sides of the plate.
It is desirable to provide an improved electromagnetic valve actuator design which improves opening and closing speeds of the valve, reduces power consumption required to hold the valves in open or closed positions and improves valve lift profiling.
The present invention improves upon the above-referenced prior art electromagnetic valve actuators by using a unique single coil two-plate armature design in which each armature includes a permanent magnet. This design improves opening and closing speeds of the actuators, reduces power required to hold the valves in open and closed positions, and improves valve lift profiling. These factors improve volumetric efficiency of the engine at higher speeds, reduce parasitic losses, decrease noise, and enhance durability.
More specifically, the present invention provides an electromagnetic valve actuator (EVA) for actuating movement of a valve in a vehicle engine, including a valve assembly operatively connected to the valve for movement therewith and including a shaft connected to the valve. Two armature plates are operatively associated with the shaft, and each armature plate includes a permanent magnet. An electromagnetic coil is positioned between the two armature plates for selectively electromagnetically pushing and pulling the armature plates for actuating opening and closing movement of the valve. Two springs are engaged with the two armature plates, respectively, for biasing the armature plates in opposing directions. The permanent magnets are operative to assist the electromagnetic coil in holding the valve in a desired position to reduce power consumption.
Accordingly, an object of the invention is to provide an improved electromagnetic valve actuator including a single electromagnetic coil which actuates two armature plates which each include a permanent magnet, thereby improving opening and closing speeds of the valve and reducing power consumption.
The above objects and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.